In Iraq, the city of Tikrit and the areas around it are at the center of an ongoing battle. Sunni extremists with the self-proclaimed Islamic State took over the predominantly Sunni area in June. Now Iraqi security forces and allied militias are trying to drive ISIS out. Most of these forces are Shiite and backed by Iran, and some have a record of revenge attacks on Sunnis, but NPR's Deborah Amos spoke to local Sunni tribesmen who have unexpectedly joined the Shia.

DEBORAH AMOS, BYLINE: Ali Al Jabbouri agrees to meet here in northern Iraq a few hours before he heads for the battlefront. A member of a prominent Iraqi tribe, Jabbouri is also the mayor of a city of 100,000, Al Shargat, now occupied by ISIS militants.

And tomorrow, you are going to change from your suit and...

MAYOR ALI AL JABBOURI: I am soldier in army - (laughter) my army.

AMOS: His army is a tribal force, more than a thousand men. This graying city mayor has reason to fight. Eighteen of his relatives are dead, including his brother, killed by militants in June. His city is a victim of ISIS and the map. Located on a highway between two larger urban centers, ISIS sees Mosul first, then swept down the highway towards Tikrit, grabbing Al Shargat along the way. ISIS declared Ali Jabbouri's city as part of the so-called Islamic caliphate.

JABBOURI: Yes. My city.

AMOS: Recently, more militants have showed up as pro-government forces hit Tikrit. Some ISIS fighters are retreating north.

JABBOURI: They left Tikrit and come to Al Shargat - the ISIS.

AMOS: So that's why you're going back to fight?

JABBOURI: Yes. So that I go to Al Shargat to kill any ISIS.

AMOS: A decade ago, the Jabbouri tribe fought militants alongside Americans. Many joined the awakening movement organized by the U.S. military. This time, Jabbouri says he's fighting alongside Iran and Iraq's Shiite militias. It's a surprising alliance considering Jabbouri was once an officer in Saddam Hussein's army fighting against Iran, and many Sunnis are especially wary of their powerful Shiite neighbor. But times are different, he insists. Iran is willing to put boots on the ground.

JABBOURI: (Through interpreter) Yes, that's right. I was in the Iraqi army, but you have to know what - when ISIS come, we just need help for anyone - America, Turkey, anyone. No one help us. Iran help us, and it's fine. Iran help us. No one help us. America don't help us.

AMOS: Iran is helping and backs Iraq's Shiite militias, but there's a major snag as pictures of Shiite revenge attacks against Sunnis emerge. One particularly gruesome image - a Shia militiamen posed with the severed head of an alleged ISIS fighter and posted it on Twitter. A Human Rights Watch report this week documents looting and burning of civilian homes in Sunni villages. Washington has warned of funding cuts if the militias aren't reined in. Analyst Zaid Al Ali says that Baghdad has finally gotten the message.

ZAID AL ALI: It seems to be the case now that the government is kind of getting its act together.

AMOS: The Prime Minister publicly condemned the abuse and warned of severe punishment if it didn't stop. It's a crucial message for the major battles to come, says Zaid Al Ali, author of "The Struggle For Iraq's Future." Sunnis in ISIS-controlled Mosul are all watching what happens in Tikrit.

ALI: If there are terrible abuses in Tikrit, then of course ISIS will thrive on that, and they'll tell people in Mosul, this is what's going to happen to you, whereas if people are allowed to go back home in Tikrit and the city doesn't suffer terribly, that send a very powerful message to Mosul that this is the right side of the battle.

AMOS: This Iraqi police general, also a Jabouri, believes he's on the right side of the battle. Ali Jabouri is a Sunni Arab fighting ISIS along with Iraqi Shiites. Still, the Jabouri tribe represents a minority. Most Sunnis haven't risen up against ISIS yet out of self-interest or out of fear or because they see the Shiite militias as worse. General Jabouri says he knows Washington has complained about the abuses.

ALI JABOURI: (Through interpreter) Yeah, sure, I heard this. But I don't think they have the full picture. I want to say, everyone knows who's ISIS. In my area, I know who killed my brother. But I'm not going to make any trouble with civilians. Now maybe the militias don't know that.

AMOS: These Shiite militias and the charges of abuse are now a concern across Iraq. But for these members of the Jabouri tribe, the fight against ISIS is a higher priority. Deborah Amos, NPR News, Erbil.

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